1. Field of the Invention
The present invention relates to compensation device applied to a power amplifier and a related method, and more particularly, to a compensation device and a related method for determining pre-distortion amplitude values and pre-distortion phase values of the power amplifier according to a predetermined gain of the power amplifier, a power input signal with different amplitude intensities, and a receiving signal corresponding to the power input signal.
2. Description of the Prior Art
In today's integrated circuits, power amplifiers have been widely applied to various kinds of application circuits, such as a communication system. Generally speaking, a power amplifier can be used as a gain stage for amplifying an input signal. However, the linearity of the power amplifier is not ideal in practice.
Please refer to FIG. 1 (including sub-diagrams 1A and 1B), wherein 1A is a diagram illustrating an amplitude modulation distortion curve (AM-AM curve) of a power amplifier, and 1B is a diagram illustrating a phase modulation distortion curve (AM-PM curve) of a power amplifier. As shown in 1A, when the power amplifier operates under a linear region, the amplitude gain of the power amplifier is approximately maintained at a fixed value. When the power of an input signal is continuously increasing, the amplitude gain of the power amplifier will be decreased instead, which is namely the so-called AM-AM effect. As shown in 1B, when the power amplifier operates under a linear region, the phase of the power amplifier (i.e., the phase between the power of the input signal and the power of its output signal) is approximately maintained at a fixed value. When the power of the input signal is continuously increasing, the phase of the power amplifier will be changed (decreased) instead, which is namely the so-called AM-PM effect. As one can see, the AM-AM effect and the AM-PM effect occur when the power amplifier operates under a non-linear region.
However, users usually hope that operations of the application circuit (s) are linear operations, and thus there are multiple relationships existed between all parameters. If the application circuit operates under a non-linear region, it may induce many harmonics and affect other channels. In this way, it may result in a poor communication quality.